The invention relates to actuators and zone valves for heating and cooling systems.
Zone valves are often utilized in hydronic heating and cooling systems. The zone valves isolate specific areas or "zones" of the system. Typically, each zone valve is controlled by a thermostat, which causes the valve to open and close to achieve desired temperature changes.
Conventional zone valves are typically actuated by either a heat motor or an electric motor. In valves with a heat motor as the actuator, an electrically heated element causes linear movement of an actuating element that, in turn, opens the valve. In valves with electric motors, the motor and associated gears move a valve member between closed and open positions (e.g., a rubber plunger moved away from a seat or a ball element moved through a 90 degree rotation).
Conventional motorized zone valve actuators employ a motor which is energized in one direction by a source of power, held in some predetermined position by a mechanical or electrical braking means, and then returned to its original position by a spring.
Giordani, U.S. Pat. Nos. 5,131,623 and 5,540,414, describe zone valves for hydronic heating or cooling systems in which a motor-driven actuator rotates a ball valve through about a 90.degree. rotation, between closed and opened positions. The motor rotates the valve from its normal position, which may be either open or closed, to the opposite position, e.g., if the valve is normally closed, from the closed to the open position. When the motor is de-energized, the valve is returned to its normal position by a spring so configured that it provides sufficient restoring torque to overcome the frictional torque of the ball valve.
Carson, U.S. Pat. No. 3,974,427, discloses a motor control apparatus having an electric motor which is driven in one direction by an alternating current power source and in the opposite direction by a spring. Holding or braking of the motor is accomplished by applying a source of direct current power to magnetize the motor and hold it in a predetermined position after the alternating current power source is removed. This holding or braking action is removed by taking away the direct current power source and momentarily applying an alternating current power source to the motor, thereby de-magnetizing or degaussing the motor so that it is free to return to its initial condition under the power of the spring.
Fukamachi, U.S. Pat. No. 4,621,789, discloses a valve mechanism in which the valve is prevented by a physical stopper from moving any further after it has moved to an open or closed state.
Botting, et al, U.S. Pat. No. 5,085,401, discloses a valve actuator in which the motor makes an electrical contact after rotating a predetermined distance, causing deenergization of the motor.
Fukamachi, U.S. Pat. No. 4,754,949, discloses a valve actuator in which the rotation of the valve by a predetermined amount causes electrical contacts to be turned off, stopping the rotation of the actuator motor.
Some motorized valve actuator systems employ a fail safe energy system to provide power to the actuator motor in the event that the main power source is lost. Strauss, U.S. Pat. No. 5,278,454, discloses an emergency, fail safe capacitive energy source and circuit which is used to power an air damper actuator or a valve actuator. A sensor detects loss of power to the valve actuator circuit or motor, activating a switch which connects a bank of capacitors to the motor, with the appropriate polarity to drive the actuator back to its fail safe position. No provision is made for interrupting the connection between the capacitors and the motor when the fail safe position is reached, and thus the motor appears to work against a mechanical stop defining the fail safe position.